1. Field of the Invention
The invention is directed to unshaped refractories having a carbon bond, which refractories are used as hot-gunning mixes for repairing and lining converters, as tap hole mud, and as runner and trough material for molding by use of vibration to provide the runner or trough used for discharging pig iron from blast furnaces, which unshaped refractories exhibit particularly excellent erosion resistance.
2. The Prior Art
It is known that carbon is effective to prevent slag, molten pig iron or molten steel from entering into the structure of refractories. One example is the brick used for converters, which brick is impregnated with tar. Another example is the nozzle stopper for a ladle used to pour ingots. Currently, a number of workers in the art have been directing their efforts toward the use of carbon to prevent slag, molten pig iron or molten steel from entering into the structure of refractories and, in particular, efforts have been made to use carbon for this purpose in such refractories as hot gunning mixes (gunning mixes) for converters, and runner and trough material (runner material) for vibration molding of the runners used for discharging pig iron from blast furnaces.
One such endeavor is disclosed in Japanese unexamined patent publication No. 17506/73, which is directed to refractory material for runners used for discharging pig iron from a blast furnace. In this publication, a refractory aggregate controlled in particle size is mixed with 10-30% by weight of hard pitch of medium grain size (0.07-1.0 mm). The refractories described in this publication are ones in which crushed hard pitch and aggregate is mixed by a mixer.
Japanese unexamined patent publication No. 127413/77 is directed to a method for repairing the walls of furnaces, such as converters, in which the surface of granular bodies is coated with a high softening point pitch. A quantity of separately prepared granules also coated with pitch of the same high softening point quality is granulated to the size range 0.2-2.0 mm. Less than several percent of the latter granules is added to and mixed with the earlier formed granules and the mixture is gunned to the walls by use of a dry gunning machine. In the hot repairing of furnace walls as disclosed in this publication, a complicated manufacturing process for covering the refractory granular bodies with pitch is required and it is difficult to make a uniform covering. As such, the components, when adhered to the walls of a furnace, are non-uniform and no particular improvement in erosion resistance can be actually demonstrated.
Japanese publication No. 27049/67 discloses refractory compositions for use as gunning mixes and stamping material in which the compositions comprise substantially non-acid refractory particles, 2-12% solid pitch particles, 0.05-4.0% of a plasticizer and 0.5-5.0% of a water soluble cold setting bonding component. The solid pitch particles are chosen to have a softening point of at least 200.degree. F. (93.3.degree. C.) and a particle size such that substantially the entire amount of pitch particles pass through a 4-mesh sieve and a substantial amount of particles are retained on a 100-mesh sieve (the sieves being standard Tyler mesh sieves).